Superregenerative receiver system



Nov. 28, 1944. M. G.. CROSBY SUPER-REGENERATIVE RECEIVER SYSTEM Fled March 6 1943'- .Ail L: .www

, generically either frequency modulated (FM) carnature.

from the aforementioned Patented Nov. 28, 1944 c UNITED N STATE-S PATEN Toreros SUPERREGENERATIVE RECEIVER SYSTEMY Murray G. Crosby, Rive rhead, N.` Y., assignor to;

`Radio Corporation of America, a; .corporation of Delaware Application March 6, 1943,` Serial No.v478,254

, 13` claims. (o1. 25o-,20)

My present invention generally relates to super-q regenerative receiving systems, and more particul larly to a super-regenerative receiver of` angle modulated carrier wave energy.

In the past there have been proposedfvarious circuit arrangements for receiving angle modua receiving systenr` lated carrier wave energy with employing super-regeneration; By the `term angle imodulated carrier `wave energy is meant rier wave energy, phase modulated (PM) carrier in modulated high frequency energy to `be detected is first `applied to as`uperreg"enerative amplification stage,` and subsequent to such amplification is applied to an infinite impedance detector to s produce the modulation signals. Y The novel featureswhichl believe to be characteristic of my invention are `set forth with particularity in the appended claims; the invention itself,` however,`` as `to both its organization and wave energy, orhybridsthereof. The prior cir-J i cuit-arrangements have generally utilized `a .pair of super-regenerative detector tubes whose respective input electrodeswere presented1with sloping filter characteristics of complementary A super-audible quench oscillator s applied the super-audible quench oscillationstoj the detector tubes in alternate sequence. `Various disadvantages exist in such prior arrangementsL" For example, the possibility of `oscillation between the quench oscillator and the detector output circuits exists. Again, the super-regenerative detector tubes may be inadvertently coupled together thereby preventing `proper discrimination ofi the method offoperation will best be vunderstood by reference` to the following description, taken in connection with the drawing, inwhich'I have indicated diagrammatically al circuit organization whereby my invention maybe carried into effect. `Inthe drawingV I I s i l Fig.` 1 shows a circuitdiagrami of a, receiver embodying theinvention, l

Fig. 2 graphically `illustrates `the resonance `curves of the input circuits of the super-regenerative oscillators. j

Referring `to Fig. 1 of the '.drawing, the numeral I designates a" signaliinput transformer Whose coupled primary and secondary. circuitsZ and 3 I are each tunedto the carrier frequency of applied anglemodulatedicarrier wave energy appliedto the detector tubes.

\ `It may.

the main objects of my present `invention to pro` vide a supereregenerative receiving system Vof angle modulated carrier wave energy which is free disadvantages, and which offers all the advantages whichfexist when utilizing super-regeneration in a receiving system i f Another important object of mylinvention is to provide a super-regeneifative receiving system for modulated high frequency carrier energy,` Wherein the received modulated carrierenergy is ap#- plied to a pair of super-regenerative oscillator ciramplifier coupling `tubes between the point of oritherefore, be stated that itis one of l mary circuit 2 could bel Vmodulated high `frequency signals.` `These applied signals may be FM signal energy, or AM signal energy. `Indeed,4 as stated heretofore,.th`ey may be PM signals. `The receiving systemvmay be of thesuperheterodyne type. Thatis to say,the signal energy fed to transformer I from prior circuits couldlbe subjected tov prior superheterodyning so that the signalenergyapplied to the pris of Lan'intermediate` fre-` quency (I`.IF'.) Further, the signal energy applied to vtransformer I lcould (kc.) range, or in the `megacyclelmc.) range. j For the purposes of the presentapplication, let it be assumed'- that the signal` energy applied to transformer I has been reduced to an I. lalvalue,` and that, therefore; each `of circuits 2 ande is xedly tunedto the `operating I.;;F. value. H

. `Todemodulate the` applied signal energythere is provided apairof `detector tubes 4 and 5. I'hese detector tubes are connectedin `infinite imped-` ance detector circuits. `Thistype of detector circuit is `very well known to those skilledin the art,

and the theory of `operation thereof need not be described in detail. t It is gin` of the FM signal `energy and the off-tuned input circuits of the oscillators whereby the aforementioned mistuned inputf circuits are isolated` from each other. s

Still another object of my invention is tovprovidea super-regenerative.receiving system where` in detection is accomplished in astage distinct I from `that; `of super-regenerative amplification.

Yet `another object of` the invention is to provide a super-regenerative receiving system where;-

sufcientqfor the purposes of this application to .point` out `that the `cathode of each of the dtector` tubes 4 and 5 is connectedto ground through a cathode resistor which is by-passed for radio frequency currents,

but `not forthe modulationfrequency currents. y

Y 1 Accordingly, the cathode-of tube` 4 is connected AUl `bypassed by condenser'l the radio frequencyy currents.1; Hence, there is deto ground through resistor 8, `and the latter `is which bypasses solely .velopedaudio frequency `voltage acrossresistor 8 which is appliedl in :degenerative phase to `the control grid 8- byI virtue ofxthe'grounded grid re-v 3 beweither in the `kilocycle l s -nating condenser I 5.

' FM signal energy.

turn resistor 9. The plate I of tube 4 is connected to a point of positive potential of a direct current source (notshown). The tube functions in the same manner as tube 4, and, hence, the corresponding `circuit elements are indicated by a prime indication. It is suflicient to point out that by virtue of the audio degeneration across each of resistors 6 and 6', each of these tubes functions in the manner of a diode whose space current flow is regulated by a 'control grid. Another name for this type of inniteimpedance detector is degenerative plate circuit detector. This type of detector is used in order to minimize the loading of the super-regenerative amplifiers which feed the respective detectors.

Y The signal energy is applied to the control grids 8 land -8' by meansof respective coupling condensers II and II'. Each coupling condenser is connected to its respective superregenerative oscillator circuit. The functioning of each oscillator circuit is to provide the advantage of superregenerative amplification without encountering the disadvantages which y'arise when super-regenerative detectors are used. Considering, first, .the super-regenerative oscillator circuit to which lcoupling condenser II is Aan electron dischargetube I2. lshown by way of illustration as consisting of a connected; it comprises The tube I2 is triode, but the inventionis not restricted to this type of tube. high potential` side of the resonant input circuit. The latter consists of coilI4 shunted by a reso- The cathode I6 of tube I2 is connected to ground, a predetermined intermediate point I1 on coil I4 being returned to the l sociated :circuits lprovide an oscillator. of the Hartley type. The input circuit I4-I 5 is tuned to a frequency F1, which is on one side of the mean i .of the applied FM signal energy. The coupling condenser IIis connected to the high. potential side of the input circuit I4-I5. Hence, it will be seen that the super-regenerated frequency Fc vsignal energy` developed across -circuit I4-I5 is p applied through -condenser II to the grid 8 of the infinite impedancedetector tube 4.

l Since the second super-regenerative oscillator circuit is an exact duplicate of the first, the corresponding .circuit components are indicated by l prime indications. The input circuit I4'-I5' of oscillator tube I2 is tuned to a frequency F2, which is on the opposite side of the mean frequency Fc. The relation between the resonance curves of circuits III-I5 and I4'-I5' is shown in Fig. 2. It will be seen that the peak frequencies of these input circuits are located at frequencies F1 and F2. The cross-over frequency of the two resonant curves is located at Fc. The tuning condensers I5 and I5* are, of course, adjusted so that the cross-over frequency Fe shall loe-equal to the mean frequency of applied FM signal energy. Where desired, the frequency spacing between peak frequencies F1 and F2 will exceed the maximum frequency deviation ofthe The grid 8.",of Ainfinite impedance detector 5 is connected to the 'high potential side of input circuit kI.4'--I5' by the-'coupling condenser II". In order- Atollisolai'lethe .input circuits of the oscil- The plate I3 is connected to the lators. the signal input transformer I is coupled to the two input circuits lI--IB and I4'I5 through a pair of amplifier coupling tubes. The advantage of using separate coupling tubes to feed the two olf-tuned circuits is that the ciftuned circuits are isolated. This means that they are not coupled together, and can be separately detuned as shown in Fig. 2. The coupling arnplifiers may be of any well known type. Merely by way of example, they have been shown as pentode tubes 2| and 22. The signal input grids 23 and 24 of tubes 2| and 22 respectively are connected in parallel to the high potential side of the secondary circuit 3.

The cathodes of tubes 2l and 22 are connected to ground through their respective gridl biasing networks.. The plates of the coupling tubes are connected to the +B terminal of the direct current source through respective radio frequency choke coils 2l and 22. The direct current blocking condenser 25 couples the plate end of choke coil 2| to the high potential side of input circuit I4-I 5. The direct current blocking condenser 25' couples the plate end of choke coil 22 to the high potential side of input circuit I4I5.` It will now be seen that each coupling tube ampliies the signal energy applied tothe signal grid thereof. Tube 2I will transfer its'amplied signal energy t0 the input circuit 1 I4-I5 of oscillator tube l2. In the same way the coupling tube 22 will transfer ampliedsignal energy to its associated input circuit I4-I5 of oscillator I2. Hence, there will be substantially no coupling between the input circuits, and their oppositely-mistuned relation will be maintained in the manner desired.

' The super-regenerative functioning of the oscillators I2 and I2 is secured by virtue of the quench oscillator circuitl which comprises tubes 3|!v and 30. The cathodes of the two tubes are connected in common to ground. The control grid 3I is connected to control grid 3| of the opposite tube through a pair of series-related grid return resistors 32 and 32. The junction of the grid return resistors is connected to ground. The plate 33 of tube 30 is` cross-connected togrid 3|v by means of the coupling condenser 34, The plate 33 of tube 30 is cross-connected togrid 3| by coupling condenser 34. The plates-33 and 33' are connected together by the inductance coil 35 of the oscillator circuit. Themidpoint of the latter is connected to the +B terminal of the direct current source through a radio frequency choke coil 36. The lower end of coil 35 is connected byvlead to the tapping point I'I" on oscillator coil I4'. The lead 4I connects the upper end of oscillator coil y35 to the tapping point I'I on the oscillator coil I4.

It will now be seen that the quench oscillations are injected into the tank circuits of' the tubes I2 and I2'. It will also be appreciated that the quench oscillatory energy is applied into the plate circuits of the pair of super-regenerative oscillators. Plate injection is employed in order to prevent spurious oscillations such as arise with grid injection. The quench oscillations are pre`ferably at a superaudible frequency. It is not believed necessary to describe in detail the manner in which the application of the quench oscillations to theoscillator tubes I2 and I2 results in super-regenerative amplication. It is suicient for the purposes of this application to point out that high sensitivity and gain are secured at the oscillator tubes I2 and I2 as a result of the alternate application of the quenchy oscillatory en# ,lination of i the 'quench `2,363,651 'ergy'to the oscillator tubes I2and IZ'wEvenif i yeryweak signals are applied tothe input circuits of these-oscillator tubes, yet there willibefsecured va high degree of amplification by virtue of the super-regenerative action due to the alternate superaudible quenchingof the `oscillator tubes l2 and`l2. v

"However, demodulationfatrtheoscillator tubes` 42,12'` `is not utilized. IInstead, the function of V"detection takes `place` at the infinite jimpedance detector tubes4 and 5. By separating the function'sfof amplificationand detectionthere is pre-V ventedithe possibility. of oscillation between the `quenchoscillator tank circuit "and the detector .plate circuits.` `'I'he radio frequency super-regenerative oscillations are fed tothe infinite im,

` `pedance detectors through capacityQresistance coupling, and, hence, the quench frequency currents will not pass to the detectortubes 4 and5. "There isthen `securedthe dual advantage of elimomission` of transformer coupling between the super-regenerative oscillators and theidetector `circuits.` "It is pointed out that the tank circuit of the quench Furthermore, "so designed as to fpass the oscillatory output of `tubes l2 'and l2', but `not the currents of quench In place of the" specific detectors frequency. shown, there may `be used diode rectifiers.

The audio voltage developed across each of "cathode load resistors Sfand E' is applied to a. Arespective audio `amplifier by `resistarice'-capacity coupling. Thus,` the grid 52 of audio amplifier ltube 50 is coupled by direct current blocking con l denser 5| to the cathode end of resistor `6. The grid `52 is returned to ground by resistor 53. Bias frequency current, and i oscillator comprises coil 35 in asso- ,'-ciation `with the bypass condensers" I8 and I8'. v the networks II-9 and l\l'.-9' are` `the detected Fig. 2 shows that the off-tuning of circuit iii-l 5 will be compensated for bythe' opposite off-tuning of circuit outputs of the infinite impedance detectors 50 and 50. The amplified audio `signal voltage will be added in push-pushrelation` at transformer T. If`desired`,iinput circuits: ill-l5 ceiving AM waves.

i `While I have indicatedand described a system for carrying my4 invention into effect, it will be apparent to oneskilled-in the art that my invention `is bynomeans limited to theparticular organization shown and described, but that many the appended claims.

`coupling said detector WhatIclaimis:` f i 1. In a lsignallingsystem,atleast one oscillator tube circuit, means for applyingmodulated radio signals thereto, means for quenching thefoscillator at `a superaudible frequency to provide super-regenerative amplification, a detector of the infinite impedance type coupledto the oscillator for deriving the modulation Isignals and purely1 capacity-resistance means coupling said oscillator thereby to prevent `quenchcurrents from passing to the detector. y

"2. In a signalling system, at least one oscillator `tube circuitpmelans for applying modulated radio detector to said signals thereto,A means for quenching the oscilflator at `a `superaudible frequency; to provide `super-regenerative amplification, a detectorcoupled to the oscillator for deriving the modulation signals Aand purely capacity-fresistance means `to said oscillator` thereby to prevent quench currents from passing to the is Supplied the grid 52 by cathode biasing resistor Y 54. The audio tube `54) is constructedin the same manner asfamplier tube` 5D; the circuit elements pertaining thereto are designatedby cor- The" plate circuits of tubes 'responding numerals with prime" designations.`

S 'connects the primary Ywindings $0 and 6 of output transformer T in push-push relationwhen adjusted to contacts A; The push-pull relation is secured byA adjustingtheswitch to contacts B. audio utilizing networkmay be con- -Any desired nected "tothe secondary of the output transformer. i

` and 50 "may bei; connected in push-pullforin push-push: Switch detector, said oscillator circuit comprising a'tube "havinga tank circuit connected "in the plate oircuit thereof, and said connected to said tank circuit.

i When receiving `FMsignals the outputs of the amplifiers a`nd 50' should be combined inpushpull relation, since the super-regenerative oscillators lzandl" present oppositely sloping filters to thedetectorsras shown in Fig. 2. The alternatequenching ofthe oscillators causes the oscillatoryoutput thereof to be delivered to the re- I s'pective detectors in the forinof highly ampli- -ed signal-modulated modulation of the` energy is-AM at each detector input electrode, because of theaotion of each offtunediscriminator 'circuit |`4'I5 and l4'`-hl5. The discriminatoryjaction is too well known to require further description.

oscillatory energy. `The When receiving AM carrierfenergy, switch S is V thrown into"A` or push-button position. The plate circuitsof tubes 50 and 50 are now in aidingr," or push-push, relation. j The mistuning of circuits |4-l5 and I4' `|5 will not affectthe amplification by `tubes`l2 and I2'. The AMsignals will have a carrier frequency of Fc, the mean frequency of F1 and F2.

Therefore, the average output of the amplifiers I2 and I2` will be atFc;

` quenching said amplifiers thereby to render them` operative as super-regenerativeramplifiers, a pair "oppositely `mistuned i amplifier having a 3; In a frequency modulationreceiving system,

apair of regenerative amplifier Icircuits",each` a respective `signal input 1tuned amplifier having circuit, said signal `input tunedcircuits )being with respect to apredetermined frequency, `means for applying frequency modulatedfcarrier energyto said respective input circuits, the center frequency of the applied energy being equal to said predetermined frequency, a quench oscillator for alternately quenching said amplifiers thereby'jto render them operative as super-regenerative amplifiers, a pair of infinitel impedancedetectors, means coupling each respective of` infinite impedance detectors, `meanscoupling eachrespective ampliiierinllut circuit to a respective one of said infinite impedance detectors,

means for combining the detected outputs of said detectors in a predetermined relation, `and said` modifications may be made Without departing` *from the scope of my invention, as set forthin quenching means `being amplifier input circuit to a re i spective one of said infinite impedance detectors,` j `and means for combining the detected outputs modulation` receiving system,

frequency of the applied i a switch which is outiputs `in push-pullprela-tion for .frequency modulai =ti0n reception, or `in push-push 4relation for amplitude .modulation reception.

5. Ina signalling system, atleast one voscillator 'tube circuit, -means `for applying frequency vmod 4.ulatedradio signals thereto, means for quenching the oscillator at a superaudible frequency to pro.. videfSuper-regenerative amplification, a detector lof the infinite impedance type coupled to the .oscillator for deriving the `modulation signals, ya vsecond .oscillator tube circuit, said two oscillators fheing yoppositely ymistuned relative to the mean frequency of the applied radio signals, said quenching means acting on the two oscillator tubes in valternate manner, and va, separate inflnite impedance detector coupled .to the second `oscillator yand purely ycapacity-resistance means coupling each detector to its respectivefoscillator.

6. .In a frequency modulation receiving system, a pair of regenerative :amplifier circuits, each `'amplifier .having a respective ksignal input tuned circuit, said sign-alinput tunedcircuits being op,v ,-positely mistuned with respect to a .predetermined frequency, means for applying frequency modulated carrier energy to said respective input circuits, .a quench oscillator for alternately .quenching said amplifiers thereby to render them operativeas super-.regenerative ampliers, a pair 'cuits being `cppositely mistuned with -respectto ,a

:predetermined frequency, means for applying modulated carrier energy to'said Vrespective input circuits, ythe .center frequency of .the applied energy being equal .to said predetermined frequency, la lquench oscillator for alternately quenching said amplifiers thereby to render'them :operative assuper-regenerative amplifiers, -a 'gpair of detectors, means coupling.- each respective am- Apli-er input circuit vto a respective `one of said detectors, andV :combining 'means including a switch 'which vis adapted to selectively combine said detected-outputs in push-pull relation for frequency modulation reception, -orfin push-push relation for amplitude modulation reception,V

10,In la 'receiving system, a pair of regenerativefamplifi'er circuits, each amplifier havin'g'fa respective signal `input tuned circuit, said signal input tuned circuits `being -oppositelymistuned with respectto apredetermined frequency, means 'for applying modulated 'carrier energy yto said respective input circuits, a quench oscillator con,- structed and arranged Afor alternatelyv quenching said amplifiersxthereby to render them. operative as `super-regenerative amplifiers, a pair, of :de-

` tector-s, quench current blocking fmeans coupling of detectors, means coupling each .respective am-l plier input circuit vto a respective one .of said detectors, :andameans .for combining the detected Outputs .of said detectors in push-pull relation.

7.. In lan .amplitude modulation receiving sysy."

tem, apair of regenerativearnplier circuits,'each amplifier [having a ,respective signalinput tuned circuit, .means fork applying modulated carrier energy Dto said .respective input circuits, said am- .plier `input circuits .being .oppositely mistuned .L

relative to a reference frequency, a quench oscillator for alternately quenching. Vsaid* amplifiers thereby 'to render them operative as super-regen- .erative amplifiers, a pair of infinite impedance detectors, means coupling .each .respective amplierinput .circuit to a respectiveione of said in- .nite impedance detectors, means vfor combining .the .detected outputs of said detectors, said combining means includinga switch which is adapted to selectively v combine .said detected -outputs .in i

,push-.push relation for amplitude modulation reception.

8. In areceivingsystem, `a pair of regenerative yamplifier circuits, each.amplier having a respec- -tive ,signal input tuned circuit, said signal input tuned circuits being oppositely mistuned with reF .spect to a predetermined frequency, means for applying modulated carrier energy to said respective linput circuits, lthe center frequency lof the appliedenergy being equalV to said predetermined frequency, .a quench .oscillator for alternately ,quenching said .amplifiers thereby 4to render them operative as superregenerative amplifiers, a `pair .of detectors, .means coupling each .respective amplifler .input `circuit `to .a respective one of said detectors, .and means ,for .combiningthe detected outputs of Asaid .detectors in ,a predetermined relation.

L9. .'Inan anglemodulated carrierenergyreceiving system, :a .pair of regenerative amplifier circuits, ,each van'iplifler having .a respective `signal input ltuned circuit, .said signal input tuned. cireach ,respective amplifier to a respective one v-f said detectors,` and means for combining the .modulation outputs of `said detectors in a predetermined-relation. j Y

11. In a receiving system, a pair of regenerative amplier circuits, yeach amplifier'vhaving a vrespective signal input tuned `circuit, ymeansgfor applying :modulated :carrier energy Vto said respective input circuits, a yquench oscillator -con- ,structed Vand arranged for valternately quenching .said amplifiers thereby to render them `operative ,as super-regenerative amplifiers,` a pair yof `detectors, means couplingeach respective amplifier input vcircuit to a respective-one of said detectors, Ya switch connected to the output circuits of the detectors adapted selectively `.to combinethe'detected `outputsi-n :push-pull relation for vfrequency rmodulation reception, or in push-push .relation for .amplitude modulation reception.

12. In a signalling systemya pair of oscillator .tube circuits, a discriminator networkcoupled to ,said :oscillator tubes, means for applying .frequency modulated lradio signals to said discrim inator network, means for alternately lquenching the -oscillator circuits .at a -superaudible frequency to provide super-regenerative amplification, and ,a respective detector separately,` coupled-.to :said discriminator network for deriving the modulation signals.

13. In a receiving system, a pair of regenerative ,am-plier circuits, each amplifier having a respective signal input circuitysaid signal input circuits providing sloping filter characteristics-of complementary nature, means for Vapplying modula'ted carrier energy to said respective input circuits, the .centerfrequency of the applied energy being `equal to the `cross-over frequency of the characteristics, a quench oscillator -for alternately .quenching said amplifiers `thereby to render them operative as super-regenerativeam- ,plii-lersa pairiof detectors, means couplingeach 

